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(RNN) – Russian aggression is likely not over in the Ukraine, said one foreign policy expert.

"(There is) a strong possibility they will invade eastern Ukraine," said former Reagan national security adviser Bud McFarlane.

Russian President Vladimir Putin has amassed thousands of troops in Russia just across the border from Ukraine where they have been holding military exercises.

The groundwork for destabilizing Ukraine is already laid, says Olena Nikolayenko, a native of Ukraine and an expert on Russia. The propaganda war is already in full tilt, says Nikolayenko, a professor of international political science at Fordham University in New York. To justify an intervention into Ukraine, Putin is trying to establish that ethnic Russians living in Ukraine are being mistreated, Nikolayenko said.

"The volume and the magnitude of state propaganda on Russian TV is stunning," she said. "For example, the Russian TV Channel 1 reported that thousands of ethnic Russians are currently fleeing Ukraine, and showed images of a line in front of a border checkpoint. But Russians forgot to remove an image of the name of the checkpoint from the clip so it can be clearly seen. The footage came from a very busy checkpoint on the Polish-Ukrainian border, and there is no flight of ethnic Russians from Ukraine."

McFarlane also says there is every indication that Russia seeks to subvert eastern Ukraine and may urge for a separation referendum similar to the one just approved on Sunday in Crimea.

Nikolayenko agrees, and says that Putin has to keep in mind the yearning for democracy millions hold on to inside Russia itself. "Putin would like to gain control over eastern and southern parts of Ukraine," she said. "If Ukraine succeeds in joining the EU (European Union), it will significantly undermine the image of omnipotent Russia in the region. And it might inspire Russian civic activists to mobilize for regime change."

She added that so-called Russian "tourists" have arrived in several Ukrainian cities located within a few miles of the Russian-Ukrainian border, attempting to instigate pro-Russian sentiments and destabilize the political situation in the country. "In the near future, the Russian government is likely to interfere with the conduct of the presidential elections in Ukraine scheduled for May in order to place a Russia-friendly politician into the president's office," she said.

The energy weapon

McFarlane says there are concrete steps American and its Western allies can take to slow Russia down and empower Eastern Europe.

"Ukraine‘s vulnerability rests on its reliance on Russian gas," he said. "There are ways to relieve that. That is to find alternative sources and develop pipelines that make gas available without coming through Russia."

He said gas could be sent to Europe through Azerbaijan and Turkey, a NATO member. "That would supply that huge demand without relying on Russia," he said. He also said America needs to urge European countries to suspend the planned South Stream pipeline that would make Europe even more dependent on gas from Russia.

An opportunity for the West

Without strong action now, Russia will be emboldened, McFarlane said. Russia will move beyond Crimea and into eastern Ukraine, Poland, Hungary and Romania, he said. But Putin's aggression does present an opportunity for the West to regain its footing.

"The West – Europe and the United States – are the best hope for the principles of the rule of law, freedom, individual initiative and self-reliance," he said, adding that America needs to rally Europe and remind it of what principles hold the West together. He said failure to do so would undermine the future of those values throughout the world.

Right now McFarlane said there is not an appetite in NATO for military action, and that it would be America's responsibility to build momentum for such a decision.

He said President Obama also should use this occasion to reverse his 2009 decision to not put in missile defense systems to protect Eastern Europe. The plan, which would have put the interceptor missiles in Poland and the Czech Republic, was opposed by Moscow.

Nikolayenko said the U.S. and its allies can put the hurt to Russia and Putin's allies if they have the will. Many prominent Russians enjoy the pleasures of the West and lead a double life, she said. "Russia should be expelled from the G-8 immediately. It does not belong to the club of democratic and high-income states," she said. "In addition, Western governments can introduce economic sanctions that will penalize Putin's entourage for Russia's belligerent foreign policy. While Russian politicians publicly express anti-Western sentiments, they go shopping in Paris, send their kids to study in London, and buy assets in Europe and the United States. Western governments can freeze their bank accounts and seize their assets with the intent to investigate embezzlement or money laundering charges against them."

Putin's track record, goals

Putin seeks to bring all the former Soviet republics, with the exception of the Baltic States, under his control, Nikolayenko said. And he has been active in expanding his reach in nations bordering Russia, sometimes at the expense of America. "In addition to Ukraine, Armenia was bullied into halting negotiations with the European Union in November of 2013," she said. "The national parliament of the Kyrgyz Republic, located on the border with China, voted in favor of shutting down a U.S. Air Force base and leasing the base for the Russian troops for the next 15 years. The list goes on."

She said Putin wants to be remembered as a leader who revived Russia's greatness and restored Russia's control over Eastern Europe and Central Asia. His natural enemy is the desire most people have to live in freedom.

"Putin is obsessed with the idea of building the Eurasian Union and bringing all the former Soviet republics, with the exception of Baltic States, under Moscow's control," she said. "But it is impossible for him to achieve this goal if democratic institutions take root in the former Soviet republics because most people aspire to live in a free and democratic state. Obviously, Russia is not a democracy and it seeks to support autocrats in the region. To date, only Belarus and Kazakhstan joined the Customs Union with Russia."

Belarus is widely known as Europe's last dictatorship, and has been run by Alexander Lukashenka for the past 20 years, while Nursultan Nazarbayev has ruled Kazakhstan since the collapse of communism.

Nikolayenko led a group of Fordham students on a trip to the Ukraine in 2013, where they stayed with students from Ukrainian Catholic University, many of whom have been involved in protests in Ukraine.